Thanks for writing to us.
The exact diagnosis can be given only though direct clinical evaluation by a dentist
If there is periodontal infection
of tooth,get deep scaling and root planning done.
Use soft-bristled toothbrush and clean your teeth in back-forth and up-down motion.
Pericoronitis during wisdom tooth eruption
also can cause gingivitis.
In such cases,tooth has to be either extracted or flap overlying tooth has to be incised and removed.
If tooth is associated with caries,restoration/root canal treatment
has to be done.
Use lukewarm saline and chlorhexidine mouthrinse to gargle.
Take complete course of antibiotics too.
Hope this helps.