My son, aged 15 months, has been a thumbsucker almost since birth. Just in the last couple of days, however, he's started sucking so vigorously that his thumb is now sore, red and rough, and covered in cuts (possibly because he's got new teeth). It's really painful for him to suck, but he's addicted and can't sleep without it. The thumb never gets time to heal because it's in his mouth so much. Any ideas what I can do to help it heal or to stop him?