Thumb sucking

My 16 month old sucks his thumb whenever he has something soft to touch... blankets, stuffed animals, our cats.... anything soft. I wouldn't care except for he is causing himself sores, that are getting nasty. I lanced it last night because it was getting really infected and I am going to have to get him into the doctor today for some antibiotics.... Any suggestions on how to get him to stop??? I've tried lemon juice and hot sauce, he thought it made his thumb taste even better!!! I've tried putting mittens on him, but he just takes them off. I don't know what to do.... It has to stop as he is hurting his health!! If you ask him to take his thumb out of his mouth he will, but whenever I lay him down for nap or bed the thumb goes right back in his mouth... Help!!

I heard someone once try not letting their kid suck their thumb unless they were in their own bedroom, and the kiddo eventually quit altogether.

A friend of mine just started telling her daughter (in a funny/bossy tone) to take her thumb out of her mouth whenever she would go for a suck (ha-ha).

Both, I guess, worked well after just a couple weeks.
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He will take his thumb out of his mouth when I ask him to, the problem is when I'm not looking (and there is something soft to touch) or when he lays down in his bed he goes right back to sucking his thumb. He is bitting it so hard that it actually got infected and I had to take him in to the pediatrician to be put on antibiotics.