15 month old - manky thumb from sucking it too much...what to do plse !?

[herbgarden]

DS sucks his thumb - it has a blister type thing on the outside now and then a nasty cut thing too on the inside and as it's always in his mouth never heals.....I am at a bit of a loss as to what to do with it but feel guilty that it looks so horrid. Poor little thing.
Any ideas anyone?

My dd has sucked her thumb since she was a few weeks old and is still doing it (she is nearly 4) at one point she almost lost the nail as it got very red and sore and the skin started to peel off. I had no choice but to bandage it up until it healed, needless to say she was not happy with that at all but it did help it to heal.

Of course the minute the bandage came off she started sucking it again! Have no idea how to stop her doing it.