Welcome to HCM,
From your history it seems that due to some poisonous bite at the site you got this problem.
Now it seems that there is likely of having some infection as well.
Take some anti histasmine like Cetrizine
tablet for 2-3 days.
If swelling is more. then you may require antibiotic medicine for 3-4 days.
Apply anti histamine-antibiotic cream locally.
ok and bye.