I've bitten pieces off my tongue more times than I care to remember.
But don't worry too much. It grows back.

Every time I bit my tongue it was always the edges.

I suppoe if your piercing is in the centre of your tongue then you should be ok.
Then again, how long is your tongue, can you touch your nose?

A friend once kept the piece I bit off as a momento.
I had strange friends, don't ask.