scratched floors question, whose responsible?

I rented my condo out partially furnished.  I put in a brand new floor 7 months before she moved in.  It is a laminate floor.

I have some dining chairs that I left for him that I just powder coated the metal legs and unfortunately one of the chairs was

missing the plastic foot at the bottom that would prevent the chair from damaging the floors.  I am really upset because he scratched the floors quite a bit in one area and the only way to fix it is to pull up the wood in that area and replace it.  I don’t know how much that will cost but I’m imagining it won’t be under 1,000.00.  I did a walk thru with the tenant and he told me what happened.  I am inexperienced in leasing apartments, as this was a condo where I used to live and I have never rented it before.  I had my neighbor there with me who said in front of him that he felt the damage was my fault because my chair was broken.  I told him verbally that I wouldn’t charge him for it, but now I feel a little taken advantage of.  Why didn’t she notice that he was scratching the heck out of the floor for so long?  Why didn’t she move the chair instead of sliding it against the floor?  What is the right thing to do?  Do I need to stick with not charging her for this and pay for it myself or am I being taken advantage of by doing this?  Please let me know what is fair.

I would really appreciate it.

Anna