Finally self soothing, but I'm worried about his finger

Hi all,
ds 18 months has finally begun self soothing, which is great and I'm stoked.
It means he goes straight down when he's tired and resettles easily in the night.
The only thing is, he does it by sticking his whole finger in his mouth and sucking. Now his finger has gone all red, a bit swollen, and it's like there's a graze on it. It's not puss-y, but I'm worried it could get infected.
What do I do? I don't want to stop the self soothing, otherwise I coul use stop n grow...
Does anyone have any thoughts?
Thanks

DD1 self soothed by sucking her thumb til the start of the year when we weaned her off it, hers was always red and wrinkly, she did get a nail infection twice, we were advised to put betedine then wash off a few minutes later so she didnt suck the betedine, id just keep an eye on it!

Ok, thanks