Grrrrr! I'm almost done with a bag that I'm making for a friend (for Christmas), all I have left to do is put in the straps, then this happened…

I used a wet washcloth to wipe up some chalk marks on the denim fabric and then I saw that there was blue all it! Then, I looked at my hands, even they had a blue tint from working with the fabric. What do I do???
I washed and dried the fabric before hand and figured I was good to go. I've never encountered this problem before. Any tips or tricks on how to fix this? If I can't fix it (sure hope I can!) how can I prevent it from happening again?
Is there some kind of solution I can buy to wash the fabric in to set the dye???
Any advice is greatly appreciated!
Darn it! The bag is really cute too (if I do say so myself!).