Yes, you should aspirate if it's IM. You want the IGF in the muscle, not the bloodstream. The reason for going IM is to target the IGF receptors in the muscles you just worked. If it gets in a vein, I imagine it will just attach randomly. Probably not a total waste, but not good either.
If you draw blood, just pull out & shoot somewhere else. The blood won't hurt you. It's rare that you will draw any, but use caution.