Let me qualify my comment.
Paxista pointed out something I did not consider.
In addition I didn't actually see the injury.
Bruises on the feet tend to heal by themselves. Infections are another animal entirely.
Furthermore, antribiotics do not "travel well" and oral antibiotics don't do a lot of good for the feet.
If you are still having problems don't hesitate to have the foot looked at.
I know that such problems have a "low triage" value and recently spent seventeen hours in an emergency room with someone with a minor wound, so I was trying to spare you that.
If you suspect infection, that get it looked at.
Actually, yes, you have reason to be concerned. Pressure washers will press clothing fibers deep into your skin which frequently cause infection. I assume you were wearing shoes and socks. If, instead, you were barefoot, then Ouch!
When using a pressure washer, wear tough clothing, safety shoes (hopefully you have them or can borrow them), and eye protection. Actually read the safety labels in the owner's manual. I know, there are so many ridicuolus warnings and we are inundated with dire warnings so we become complacent. But pressure washers, blades, and most other tools mean business.
If someone else sprayed you with the washer, then use your good foot to...
Yeah you might want to have it checked out just to make sure you dont have any bruising of the bone. Those pressure washers have alot of power and can cause injury. It probably wouldnt hurt to get it checked out, just to be safe.
These problems are usually self-limiting.
Getting it "checked out" means writing a check, and there is nothing that can be done, unless you are considering a tort action.
Some high-pressure washers can actually force fluid into the skin. The detergents are sometimes mildly toxic.
There is no specific treatment that medical science can offer except time.
Elevate the foot and watch for any discoloration. If discoloration shows, then it's time to see a physician.