I am the first author of a research paper I did under the supervision of my teacher (note that I am a BSc student of computer science). My paper got accepted at a conference. Now I have to present the paper, but I am feeling nervous and thinking I might say something wrong. Can my teacher, who is credited with coauthoring, present the paper at the conference?
Yes, of course. This is normal, and often happens.
There is no expectation that a particular author presents the paper at a conference. I suspect, however, that your teacher will also have a view on the matter. Do they want you to present or are they happy to present? Have you discussed the matter with them? They will know what is best.
Finally, I would say it would also be good to overcome your nervousness and think about presenting yourself. I was in the same position as an undergraduate and made a presentation of a paper at an international conference, and I am glad I did. It was a very formational experience.
I am pretty sure that every conference I've ever been to has had several papers presented by someone other than the first author. I recall some where the presenter wasn't even an author at all. This can happen for a number of reasons-- travel visa issues, limited travel budgets, schedule conflicts, illness, etc.
However (and this is the main reason for my separate answer) I want to encourage you in the strongest possible terms to go and present if circumstances permit. In particular, you should be really clear on how the funding for this trip is handled: Air fare, lodgings, and conference fees are your main concerns.
Your ability to communicate both in writing and in presentations is absolutely vital to your career, full stop. It's not just vital to your future as an academic-- it is vital in any professional position you might hold. People usually remember who told them about an idea, even if they know they're getting it secondhand. That's just how people's minds work.
Also, after the presentation, people might want to come and talk to you about it-- this is another great benefit of conferences. You get to meet people, and even though they may be asking you about your talk, you get to ask them what they thought! This is also incredibly valuable. You may spark an idea in a listener that you'll never hear unless you're there to present and then talk to people about.
The experience of giving a talk is very valuable no matter how scary it is-- and I say this as someone who used to physically shiver in adrenaline and fear while giving talks.
I'll even give you the secret to giving a first talk: Practice!
If you can arrange to give a talk in front of a class, do it. But even aside from that, practice, practice, practice. Practice like you're trying to get to Carnegie Hall. Practice until you're bored sick of it. Practice until you could give that talk with your entire cortex removed, by muscle memory alone. Practice so you know how long the talk takes. Practice so you work out your verbal stumbles. Practice, so you can fix whatever needs to be fixed, and then practice that.
Seriously, practice: I'm (now) a decent public speaker, and the week before a new 15 minute talk, I'll probably deliver it in full about three times each day. More, the night before the talk. No matter how nervous I am, I want all that repetition to kick in.
You can do this!
And you should, if circumstances permit.
Yes, as in other answers/comments, anyone authorized by the authors can present.
Nevertheless, if you (as a beginner) have the opportunity to be the presenter, you should absolutely do it.
With my own students, I do lots of "rehearsals" for any sort of oral exam or presentation... with lots of critique-ing, revising, and doing-it-over. Yes, for such a process to be ok with everyone, there does have to be trust and understanding.