Umbilical hernia

I’ve recently gotten my gallbladder removed laparoscopically a month ago. They pulled it out through my belly button and told me I couldn’t lift anything heavy for a month , I have a 2 year old daughter and they didn’t want me to even lift her and they made an accordion for my 4 month old son . But you know being the only parent around right now I have no choice but to lift stuff . Well I have a hard ball like alittle above my belly button and I JUST now realized it when I got up from the couch to check my laundry. It doesn’t hurt It just felt alittle sore in that spot when I gotten up. How do I know for sure if it’s a hernia or if it’s just from the surgery I had a month ago. But I really don’t recall having this ball. I always feel by belly button