Once the tongue has been bitten, it swells and becomes difficult NOT TO BITE. Hopefully the swelling goes down before you chomp on it again.
There is a condition known as "macroglossia". It means over-sized tongue. You will know you have it (even a mild case of it) if you have a scalloped border on the edge of your tongue all of the time. By scalloped border, I mean that the sides of your tongue have red and whitish indentations and elevated points that correspond with the contours of your teeth. If severe cases, the tongue size can be reduced surgically. This is rarely seen.
Other cases of tongue biting is the result of narrow upper and lower arches in your mouth which hinders the movement of your tongue. Essentially, your tongue could be the right size but your mouth is too narrow so the tongue gets bit when you chew.
If you merely have a tongue biting habit, similar to cheek biting, wear a mouthguard for a couple of weeks to a month to see if you can break the habit.