Blister under Callous?

I work as a cashier and a few weeks ago I noticed my foot was hurting more and more, I thought from the looks of it it was a corn and thought so until last night, on Friday I bought the corn pads and wore it for two days and it did nothing, on Sunday I bought a scraper and scraped a good part if the callous off, it felt better, but started hurting again eventually, last night i took a look at it and it still had a la\yer of callous and what looked like a fresh blister underneath, I popped the blister and now today, I am in severe pain. Does anyone have any tips or treatments for this? or what it is?