Help!!!My 3 yr old

ZL
So my 3 yr old son has the habiit of biting his nails! ALL THE TIME! till the point his bleeds and they are suoer short! what can i do to try to keep him from doing that! I hate seeing him suffering, when his nails are super short and his crying that ot hurts! :(. I tried talking to him! Did you have this problem and how did it stop? Please help.