My little cousin scratched me on my slightly depressed red acne scar and there was a little bleeding but I cleaned it, will this affect the scar?

No. A minor scratch should not affect the ultimate scar. Use topical antibiotic regularly till it heals and then restart your scar care treatment.
No. There will be no accumulation of fibrin, granulation tissue or scar contraction. I'm glad you're being treated for you acne and hope it is effective. You'll have the option eventually of having your acne scars treated -- dermatologists have several modalities. Several hollywood male leads have kept the scars to look tough. Best wishes.