Oh this is really hard my toddler did this too. Ouch, ouch, you hurt mummy, hold a cold pack on her ouchie ... that sorta works, but not really. Once or twice I screamed in unexpected pain when I got bitten, this really scared him and he backed off a bit.

He will grow out of it at some stage, until then, just persevere. You could try "mummy prefers kisses and cuddles"!