One of my garden snails has a huge white dent in his shell is it infectious?

[Johnny]

i feel really sorry for my little snail that white dent looks painful! i really need to know if its infectious and if so what should i give him to cure it?
should i take him away from my other 3 snails?

 

[DJ EC]

put him under a micro scope baha

jokes umm i dont know!

 

[Nanthawat]

Mercy kill