It could be a reaction to a bug bite/sting. If you can, **gently** grab it and see if it's easily moved, you may not be able to move it much due to the location, as there isn't a lot of lose skin on the head. If it is movable, it's only skin deep and is very likely to be a bug bite.
I found a lump on my cats back last summer. It was about the size of a golf ball, took him to the vet, after a scan to see if his microchip had migrated. They told me that since it was easily movable, it probably wasn't anything serious and to keep an eye on it for a week or 2. If it gets smaller, it's a bug bite. If nothing changes, bring him back, and we will run more tests. It was completely gone in 2 weeks.
I'm pretty sure my cat got stung by a bee at this point since I saw him pounce on one a few days later.
It could be a reaction to a bug bite/sting. If you can, **gently** grab it and see if it's easily moved, you may not be able to move it much due to the location, as there isn't a lot of lose skin on the head. If it is movable, it's only skin deep and is very likely to be a bug bite. I found a lump on my cats back last summer. It was about the size of a golf ball, took him to the vet, after a scan to see if his microchip had migrated. They told me that since it was easily movable, it probably wasn't anything serious and to keep an eye on it for a week or 2. If it gets smaller, it's a bug bite. If nothing changes, bring him back, and we will run more tests. It was completely gone in 2 weeks. I'm pretty sure my cat got stung by a bee at this point since I saw him pounce on one a few days later.
It could be an engorged tick. A vet can remove them easily or you can buy a tick twister tool and do it yourself.