It seems you are having an abscess or boil over gluteal area. An abscess is a collection of pus underneath skin and presents itself as solid painful warm lesion with surrounding skin being inflammed and red.
I would not advise squeezing the lesion or applying tea tree oil over it.
To treat the same
Do warm moist compresses several times in a day as it will liquefy the contents inside and bring the abscess to its head leading finally to spontaneous drainage
Apply an antibiotic cream over it like neosporin
You may take antiinflammatory like ibuprofen
to settle inflammation and pain
Taking a course of oral antibiotic like cefopodoxime or amoxycillin
would help too.
All these above measures would settle a small abscess but if there is no response or the abscess is big enough then surgical incision and drainage
is the only treatment.
Hope that answers your query. Take care.