What is this on son's thumb?

[PJ67]

This started as a rough raised area on 6 yr old ds's thumb ( the soft part). He asked me to look at it tonight and it has a slight ring round the edge with a crater type hole in the centre. It's red in the centre (1st picture). The 2nd pic is after its had some sudacrem on it.

Looks like a verruca, I have one on my finger and it's been there for years now

I second the verruca. DS2 is very prone to them, and what works for us, believe it or not is to suffocate it with tape (surgical tape, electrical tape, grey serial killer-style tape, ...). It will be gone in a week. Cover it, when the tape comes off after bath, put it on again.
A friend of mine was almost in tears after her son had those huge verrucas on his foot for almost a year. When I told her about the tape during one of her visit, she told me I was mad, but she was so desperate, she tried it, and then called me to say it had worked.
No pain, no acid, no tears, no you messing with them.

Thanks. I have bought some wart gel but might try the tape. Do you leave it on all the time?

Yeah it's a wart which is basically a veruca of the hand. My daughter has a veruca on her toe. Currently using bazuka gel.

We managed to get rid of persistent verrucas using clear nail polish. Painted on daily, same idea as tape, ie suffocating it, but more comfy.