I'll hazard a guess at this (not a doctor, suprisingly!), but because you tongue is constantly in use, producing salliva, eating and so on, and being as sensitive as it is, that's probably why it's taking a while to heal. I don't think it would be anything worse than cuts, maybe ulcers, but if it's giving you a bit of distress, either physically or worrying, it can't hurt to visit a doc.