Hi!
When I had one that was as finger sized hole, I just kept it covered with a dressing, changed it everyday or when needed and let water run over it in the shower. It healed eventually

How to take an epsom salt bath, from Martha Stewart.
https://www.marthastewart.com/epsom-salt-baths-...

Hi thanks for replying, can I put the magnesium sulphate cream on if it’s already burst? I thought it wasn’t suitable for open wounds.

If I could leave the bandage off to allow it to naturally drain I would but doesn’t seem hygienic, and I’m not able to keep my arm up for a long period of time.

Yes I should have stated I put the Vaseline around the area to help it but leave the hole open.

Thank you!

Hello Gabby Claire,

Maybe try soaking in an Epsom salt bath. That stuff has to come out completely.
Magnesium sulfate is a form of epsom salt. You are already using it.

I usually don't put an oil or grease or cream or shea butter or any emollient on a draining sore.
It tends to seal in the effusion.

I put oils or creams on healing scars or to seal moisture into intact skin, AFTER it has closed up.

When a sore is draining, it seems that you want to put something drying (lemon juice, clay mask, for example), drawing (aloe vera) and/or absorbent (cotton gauze) on it.

It sounds like you are bandaging the wound up BEFORE it has been thoroughly cleaned out. It is still festering, it seems. You may have to go to a medical person to pull that sac completely out.

The thick Vaseline might be preventing it from draining or getting oxygen.
Petroleum jelly is occlusive.
Is is good at sealing moisture into the skin.

I might put that on the surrounding skin to protect it from the constant wetness from the leaking sore.
But, there must be an exit for the drainage.

Also, maybe you are using a deodorant or antiperspirant or wearing a tight or synthetic bra that is rubbing the area.

If it is worse that usual, I would see a doctor, or at least call that often useless nurse phone number or get a "telehealth" visit, mostly the same thing, but I think that their bill rate is higher.

This is not my worst area.
Maybe someone else has more experience with the underarms.
Good Luck

Disclaimer: Not medical advice.