You could get a helmet for him if he's banging his head. You should do this ASAP. My daughter used to have violent, agonizingly painful episodes, we later learned they were a type of early childhood seizures, and I wish I got a helmet for her sooner. During these seizures she would bang her head continuously for about 20 seconds or so. (It seemed a lot longer). And, it could have been the seizures but I think her head banging is what caused her to slow in her brain development. She was diagnosed with global development delay and she is still dealing with it and requires extra, modified help in certain areas in school and needed speech therapy.
I agree with everyone here that baby gates are needed in your place, or something that prevents your baby from getting to the stairs. Make sure you install them correctly.
Your exercise equipment should not be out. When I was about 3 or 4, my mom invited a friend over and her 2 young kids around my age. The girl trying out our exercise bike and her brother became fascinated with the chain gears and put his finger in the way as his sister was pedaling. You could see his bone sticking out of his finger. Wasn't a pretty picture. You should make a room where your son is not allowed in and place any equipment he shouldn't be around and keep the door closed with a baby gate.
My daughter started rolling and then started scooting backwards, crawled backwards and then learned to crawl forwards. My places was all hardwood and we would place a comforter on the floor for her "tummy time" or whenever she was playing on the floor.
We kept everything clutter free, cleaning supplies and toxins up on a high shelf in the broom closet, plug covers on every outlet, and child proof locks on the cabinets and cupboards.
A tip on babyproofing is to always be prepared for the future. Babies develop quickly One he's crawling, the next he's pulling himself up on the furniture and then he's walking and getting taller and able to get into things. Try crawling around on his level around the house and looking for hazards you may not have realized were there.
Oh, and make sure there are no large heavy objects placed on shelves or dressers, such as T.V's. There have been cases where small kids have tried to pull themselves up and the dresser and T.V. falls on them, crushing their skulls in.
Here is an important clip to watch.
https://youtu.be/pOOdmZr4Y5o