From what I understand, this is a common problem. The scar tissue heals, and you almost get a pucker effect between it and the healthy tissue.
However, since you had a major infection there, this does not rule out a recurrence. Especially since you had surgery. Did you have a shunt placed to drain the infection after surgery? If so, the shunt can sometimes act as a further conduit to infection, from what I hear.
For something like this, a follow up with your physician and surgeon is absolutely necessary. You don't want to have another infection that gets into the chest muscle or anything like that.
Good luck, you'll be fine, just get it checked out :)