Hello and thanks for the query.
It seems that you may have been bitten by an insect.
 Insects typically inject formic acid, which can trigger a reaction, including redness, swelling, pain or itching. 
In most cases insect bites cause a small itchy lump to develop on the skin.  The lump may be filled with fluid. The area around the lump is sometimes inflamed. 

In the majority of cases insect bites are successfully treated at home and clear up within a few days. 

Some people, unfortunately, react badly to insect bites.  It is useful to know what the signs and symptoms of a severe allergic reaction are

A rash, often blotchy, that spreads to other parts of the body
Breathing difficulties
Chest pain
Cramps
Faintness or dizziness
Nausea
Rapid heartbeat
Severe swelling which may be far from the bite area, such as the tongue or lips.
Very severe itching
Wheezing

If you develop any of these symptoms,then you are advised to go to ER immediately,otherwise there is nothing to worry.
 
I hope to have answered your query however you may revert to me for any other query.
Best of luck
Thanks

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