How To Treat An Insect Bite?

I was stung by a black approx 2 cm Long black as flying insect just quietly sitting on a deck listening to the surrounding peoples conversation, it was very painful & immediately swelled up, I took 2 Benadryl by mouth, the arm went numb but my breathing was not affected, after 5 days of swelling & redness the itching started and the redness and swelling did not subside, it is now 12 days later & I am finally feeling some relief, still using Benadryl gel . Was this possibly a wasp?