Okay,
1- Your piercer is meant to tell you this! Cmon guys!
2- do research before you get the piercing yeah?
But finally, if your tongue swells up until it looks as if your piercing us going to sink into your tongue, you have to go to your piercer straight away! They will give you a longer bar. If you leave it too long you have to get it surgecally removed.
Its uncommon but does happen.. about 1-500.
Trust me I am A piercer