hello and welcome to HCM,
According to your clinical history and age , i suspect wisdom tooth eruption
Wisdom tooth is the last tooth to erupt in the oral cavity and often its eruption is associated with symptoms like pain and discomfort in eating , difficulty in opening mouth , swelling in the jaws . it usually erupts in the age of 18 to 26 years.
wisdom teeth are often tilted in position and impacted in the bone , gums overlying the tooth is usually undergoes inflammation known as pericoronitis
which may lead to swelling , the flesh you can see is nothing but the pericoronal flap over the wisdom tooth that rubs the opposing teeth and makes it sore.
i would suggest you to go for symptomatic treatment at home like gargling with lukewarm saline water or antiseptic mouthwash like chlorhexidine
you can have any analgesics to relieve the pain till you consult a dentist
and get the tooth extracted surgically.
i hope this helps ,