Lump and scratch behind ear

[sardines]

Hiya,

My rattie has a bald patch with a scab behind her ear. I'm not sure what caused it as it must've happened when they were left with a friend whilst I was away. I also noticed her cage mate had really sharp nails when I came back, so I'm thinking she might have got a scratch when they were playing?
Anyway, fast forward a week since I noticed the scratch there's been a lump growing right where the scratch/scab is. Could this be just down to swelling and means it's healing or could it be something more serious? She doesn't seem to be bothered by it but I don't want to leave it be if it's something bad?

Thanks for you help!

[cyber ratty]

It could be an abscess - either let it come to a head on its own, or apply a hot saline compress a few times a day to help it. Once it forms a dark scab, it will soon lift off a little enabling you to gently squeeze out some of the pus. Continue bathing it with saline and remove as much pus as you can. The scab should come away completely after another day or two, and then just keep it clean while it heals.

[sardines]

UPDATE:
Heya,
Thanks for your help! Done the warm compresses as much as she'd let me and it went down quite quickly! Thank god! And the hairs growing back in now too.
Thanks again!