No need or advantage to punch the heavy bag bare knuckle. You will just shorten your training time by teraing your skni. It will have to heal before starting back. It is best to use bag gloves and train more effectivly, more often.

You need to use handwraps. It's just common sense. And by the sounds of it, it doesn't sound like you actually train in boxing or anything else. You just punching a bag without the correct training is quite pointless actually. Unless you just look at it like a physical activity and want to train. But you won't learn anything.

Never use bare hands on a heavy bag. You get a bunch of calcium deposits on your knuckles and have arthritic hands. Save the bare hands when and if you have to fight in a self defense scenario.

Though it can "condition" your hands, it's not wise. Like Brain F mentioned, you may end up damaging your hands in the long run.

Also some bags, depending on material, with end up scratching your hands and knuckles.

Use handwraps

I have boxing gloves but I also use just barefists on the heavy bag at times to give myself some preparation and conditioning in case I have to punch in a self defense scenario without gloves. Any advice on punching barefisted on the heavy bag? Thanks.