I know how you feel mouse.
I had similar. The pain was excruciating. It wasn't mastitis, 'just' a blocked duct.
You have to get baby feeding on it regularly. Wake her up to feed every hour or so. Point her nose towards the red patch.
Try pumping again. Perhaps after a shower?
Get a hot shower on it - I used the handheld attatchment to spray mine directly.
Comb it - a tip from my mum that worked wonders. In the shower, get a hairbrush and brush hard towards the nipple. For some reason I found that easier than hand massage.
If you feel anything other than pain - faint, fluey etc, that's a sign it's mastitis and that's when you really need the doc and the antibiotics.
I was prescribed antibiotics and it wasn't penicillin. So I'd suggest these are not the best for mastitis, if that's what it is.
I feel your pain, it's hard work bf! Your boobs will settle down soon I promise!