Can I repair those?

hello guys,

I'm new in this sub, and those are my old Timberland.
Are in quite good shape outside, but in the inside there's a problem: there's a hole that my heel "create" during the time. Is that fixable in any way possible?
I still use them normally and don't give me any particular problems, but I have the fear that this hole can became bigger and brake the outside.

I don't have a very good knowledge about shoes and Timberland, sorry.