Mag Sulph

[CrimsonElevenDelightPetrichor]

Sorry, no photos. ☹️
I have had a weird spot on my shoulder for decades; I used to be able to squeeze it periodically and get some foul-smelling gunk out of it. In the last few years, nothing has come out although there has been a definite lump under the skin. This week, unexpectedly, it seemed to be coming to a head, so I slapped on some mag sulph for a few days. Today it burst with pale green liquid and some more viscous lumps.
It still feels quite lumpy & tender. Do I keep going with the mag sulph? Or does everything always come out at once?
Apologies for the lack of photos - it's in a very awkward place.

It sounds like might be an infected sebaceous cyst. It could turn into an abcess - probably worth going to the doctor in case you need antibiotics.

It looks exactly like an infected sebaceous cyst, thanks for suggesting that @pinkgown . I've made a GP appointment but it's not for a couple of weeks. I think I'll lay off the magnesium sulphate!