Daughter having a hard time with the word "No"/consent

So last night I made a post where my husband snapped at me and I so understand where I went wrong in the situation. He's been a sahd for 4 months because he got in a horrible car accident and is no longer able to work. He's been working in construction since he was 16 and he's had a hard time adjusting. He gets horrible pains and sometimes wets the bed. We had a talk, I apologized, he apologized for snapping and today we had a conversation about our daughter. Shes 3 almost 4 and not understanding NO! She wants to be held a lot but my husband can't always hold her because of his pain and his back. He already has a hard enough time holding out baby boy. But she will jump on his back and he will tell her no and she won't stop. We had this issue at her daycare where she will jump on kids and hug them even after they say no and it ended up getting her bit at daycare. She doesn't stop no matter what. He tries not to yell at her but he does say when she will not stop doing something that physically hurts him it's hard not to raise his voice. She does that to me too and will pinch me and won't stop even if I tell her no. How can we get her to understand no and boundaries?