No worries for yourself as long as you don't swallow a flea.
I'd wait til the vet can get you something.
Some people give dewormers about once every three months on top of heartworm preventative as a precaution. This wouldn't prevent them, but would kill the worms hopefully before they become problematic. Heartworm preventatives don't cover all worms. But also some like the extra protection against hooks and esp. rounds if they have kids. Rounds are not safe around kids. I don't do this, but if I had dogs that played outside extensively, I probably would.