Hi on my bottom gum there is a bump. It is soft. It didn't hert me a first but after a while. What is it? Is it serious?

Is it like a blister? Or is it hard like a marble like som,ething is in it?

No it is soft but it is not bloody. It is located on my left side of my jaw.

It can be a blister with water not all blisters are bloody. I get blisters on my gums when I eat really hot pizza or too spicy food.

It has been there for 4 months.

If it hasn't been painful or getting worse it probably isn't abcessed. It could be a cyst,
It is best you go to the dentist and have it taken care of.

Does the bump drain and then fill up with fluid again? It could be an abscess. If it drains you won't have pain in the tooth since the pressure is released when it drains. You might want to have a dentist take a look at it. If there is an infection and it's been there for 4 months it could soon be affecting you systemically (your whole body). How are you feeling physically? Run down? Tired? Fevered? Unwell?