I have a little white bump on the tip of tongue. what could it be?

White bump: Commonly little white bumps indicate an infected taste bud. In most cases they go away within a few days, but if it does not go away have your dentist examine the area.

Needs to be seen: Without actually being able to see it, we can't tell you for sure. It could be a growth, irritation, scar tissue, or a host of other things, some benign and some not. If there is no pain and it goes away within two weeks, don't be concerned. Otherwise, see a general dentist or an oral surgeon for a definitive diagnosis and treatment or biopsy if warranted.

Irritation fibroma: From my experience this is usually a result of irritation. This being said it is always good to have this evaluated by an oral surgeon. Any form of irritation can be premalignant.