Lumpy thumb - too much sucking?!

[Jojobump1986]

DS (18m) only sucks his thumb to get to sleep but it's looking increasingly red, swollen & lumpy - like lots of blisters. Initially I wasn't too concerned about it as it doesn't seem to bother him but it's getting worse & really freaking DH out so I'm beginning to wonder if I'm being too relaxed about it! DS doesn't seem to be upset by having a lumpy thumb & I'm monitoring it incase the blisters get infected... Is there any point in going to the GP about it? I'm failing to see what they could do!

My DD sucks her thumb to go to sleep at night, she gets a little blister now and again, but it just seems to go back down after a couple of days. She's occasionally said it's sore but still pops it in and sucks away so it can't be to uncomfortable! Never looked unpleasant or got infected though!