This may be some variant of a wart just not the type you are used to seeing.there are many different types of warts.this almost sounds like planters warts I have had the same thing you described but on the bottom of my foot.Some will go "inside" some will go outside the skin.my youngest son also has what you described on the bottom of his foot.he has a docs appt next week for something else and am going to bring it up to him then(if I can remember to,lol)If you have had these for quite some time,this would be my guess but if they came on suddenly,it could possibly be something else entirely.either way,the best thing would be to see your doc about it just to make sure it is nothing more involved than warts.Let me know if you find out for sure.FB