Lump Lump under site of abscess

Hi im new so please excuse me if this is in the wrong place im looking for help. so on Friday we took our female guinea pig to the vets after she suddenly developed a huge lump within hours it turned out it was a abcess the vet was pretty poor just drained it and sent us away saying she'll be fine. A few hours later the swelling had started to return so we went back the next day and seen a better vet, this time it was drained a bigger cut was made we were giving a wash to flush the wound out several times a day and anti biotics once a day. The only thing is when the vet was examining her she said she could feel another lump under the swelling and wasnt sure what it was she sent us away anyway in the hope it was connected to the abscess. Its now Tuesday the abscess hasn't returned were still flushing it multiple times a day and giving the anti biotics but we're pretty sure the lump underneath the site of the abscess hasn't even decreased we were hoping it was just infection from the abscess but the antibiotics haven't done anything so obviously not. If it's not gone by Friday we'll be taking her back but were concerned its something sinister. Has anyone experienced this before.