I submitted an abstract for presentation in an international conference. The paper was accepted, but with a caveat. The organizers replied me that it is an abstract-only presentation. Please what do I do?
You go and present a talk. No paper will be published in the proceedings. If proceedings are published at all for this conference, your abstract will probably be published therein. This is a pretty common conference format in many engineering disciplines. You should take any review feedback, apply it to your article, and find a journal to send it to. If there is a distinction between published papers and abstracts at this conference, you should think about beefing up the paper before you send it to a journal.
I don't think there's a problem with an abstract-only presentation. Possibly the caveat is to remind you that only your abstract will be published in the conference proceedings, and not the full paper. This would work well for you as you can take the feedback at the conference and use it to improve your study. Moreover, for conference papers to be published in a journal, you need to have at least 30 percent new material (field specific); however, in your case, since you'll be presenting only the abstract at the conference, you don't need to think about these things.