I had started my PHD last year on a topic that has several interesting problem to solve in the area, however I don't find the problem interesting enough to spend 4 to 5 years. As time went by and I came across a new problem through my course work and interactions with various professors. I have started liking a different topic that is not very related to the original.
What would be a wise thing to do in such situation? Is it a common situation (changing topics midway)?