Worried about armpit lump

Last week I found a lump in my right armpit. It's round like a sphere, it feels like those small silver balls you used to decorate cakes with. Remember those? They tasted vile haha. Anyway, it's just below the skin in my armpit, it isn't up inside the armpit wall fixed or anything. I can get it between 2 fingers and wiggle it about and when I stretch the skin out it stretches with it.  I've been worried sick it's cancer because it doesn't hurt and is so firm.

Its been a week and it's not gone but it's not grown. It's still small, like those silver balls you'd decorate cakes with or a bit smaller than a petit pois pea. I was hoping it would have started to shrink but it hasn't so much mines been racing. I'm crying ruling this. It's only small but it worries me. I even fiddled with it in front of a mirror and weirdly as i wiggle it side to side between my fingers you can see it's a white small ball just below the skin. 

I have no breast lump, my breast is fine as is the other side. My breasts are small so I feel any changes easily.

Can anyone reassure me? I suffer from anxiety and agoraphobia so for me this is terrifying as I never leave my house as I have ptsd but I'm going to start working on that again after lockdown. I've spoken to my GP and she's told me to just monitor it for a couple of weeks and she said stop touching it as that'll cause it to become sore and more swollen. It doesn't hurt unless I prod for days on end so I'm trying not to not touch it.

Libby.