I've recently had treatment for breast cancer, but can only speak to my own experience with the NHS.
If you were in the UK, you'd probably get an urgent two week referral to the local breast care clinic. There, they'd examine you and maybe do some scans (mammogram or ultrasound) and possibly a biopsy.
Until you've seen the experts you can't know if it's something serious, but there's a good chance it's not.
I know this is a really horrible time as your brain will go into overdrive and you won't be able to stop yourself from worrying. The wait to find out was actually the worst part of the whole process, including treatment!
Try and stay calm, don't Google everything, and wait to see what the docs say.
If it's fine, they'll be able to tell you pretty quickly. And if it's not, you'll get the treatment you need and you can get through it.
Best of luck though, I'll keep everything crossed for you! It really is more likely to be nothing than something.