Help with my son please

hello i would like some help and advice please

My 14 year old son has worn the same White Nike socks for 1 week. He refuses to take them off and change them despite me having numerous chats with him. He has anxiety and i don’t want to keep bugging him to make it worse. He gets upset when i ask him to change them. He wears them for school and bed - and never takes them off unless having a bath, which he locks the bathroom door whilst he’s in it. 

They are white and they are dirty and stink of his sweat from being in school shoes all day and he still has no intention of changing them. its stressing me out every day.

Can i have some advice please? Thankyou