My boyfriend's 4 year old is nearly always digging her nose since I've been getting onto her about…

My boyfriend's 4 year old is nearly always digging her nose since I've been getting onto her about sucking her thumb. It's gotten so bad that this morning she had dried blood from the nostril she digs to her lip. I honestly don't know what to do other than constantly tell her to stop picking but when I do most the time she ignores me or runs off.

She is also possibly autistic (her not being tested yet is a whole other story) so telling her to blow her nose every time I catch her won't work because she doesn't know how to. I just don't know what to do but I know her nose is sore because when I cleaned it this morning she cried so the behaviour has to stop.