Dog growth / lump

[CuppaTeaNeeded]

Can anyone off any help on what this might be before we can get to the vets.

Hes had a small hard cyst like lump under his skin / fur for a while but wasn’t bothering him so we left it alone.

This morning I noticed it’s grown and changed quite a bit. It’s beside his anus but not connected / touching it. It’s hard / firm / raised. Not soft or filled liked it’s filled etc. Probably around the size of a 5p.

It can be just a growth or cancer. Is the dog old? IME old dogs can gets a few lumps and they don’t seem to have much effect on the dog or its life span.
But it could be a grass seed or similar. Animals often have really hard lumps and the pus is fairly solid inside. I’ve had sheep with blackthorn in them like this and the dog had a rock hard lump under his chin the other year, at the age of 12, we feared the worse but it was a grass seed surrounded by thick solid pus. Poor thing needed an op to sort it.

Thanks, he’s roughly 8 we believe (rescue so exact age unknown). So towards the older end for a French bulldog.