Should i be worried about a new rough spot on a three month old tooth filling?

Cracked or Bite Off: Rough spots can be caused by cracking of adjacent tooth structure, unusual wear on the filling, or a high bite where you are grinning on it, see your dentist who can evaluate the cause and correct it.

Have it examined: It may be nothing, or part of the filling or tooth may have chipped. Your dentist will know for sure after examining it.

Yes !: Go back to your dentist and have it checked. You may have fractured an important marginal area. At the least it can be smoothed.