Bumping of the head could mean your cat isn't seeing right or could be a sign of illness, I would get a vet to look at him/her
A guinea pig can obviously die if it hits its head. They are like humans, or any other animal. A small bump probably wouldn't hurt, but if it is hard enough it could injure or kill the animal.
Sebaceous Cyst.
It is hard to make a diagnosis but it could be anything from a white head to a fatty bump. If you are concerned see the doctor.
A bump is not bad. It is just an area of swelling. If it was a hard blow or you passed out at all.
everyone has this.
It could be a tumor. You should get it checked out.
A concussion is a bump large or small on someones head when they fall, get hit by an object very hard or when they get into an altercations and someone hit them with their fist.
Get it checked out by a doctor as it there are a number of causes. It is possible it is a sebaceous cyst, which is very common and easily removed.
It depends on how hard or soft you have hitted your head
Could be a concussion, or you could be suffering from shock waves coming to and from your brain. Try squeezing your fists, and then rub your temples.Anytime you hit your head hard enough to cause dizziness and vomiting you have the possibility of a serious concussion - you should be evaluated by a physician, in person.
You have a goose egg. It happens when you smack your head on something really hard.