Did I overstep my boundaries & should I apologize?

I co-signed a student Logan for my sister 10+ years ago. Loan has not been paid. They’re calling me and I settled to pay my portion of the co-signed loan to get my name off of it.
I feel it was my responsibility since I’m legal obligated.
My sister always told me she was going to pay for it, it’s been 10 yrs. and I’d like to advance in my business or buy a house, and I don’t want this loan to be my set back.