Hello sir, my buttocks are swelling (enlarged) that seems odd but at the same time, it doesn't pain at all. is there any problem with my body ?

Possible: It may be that you have some local problem there such as a cyst or some more systemic problem such as fluid (oedema) or some hormonal or skeletal problem causing distorted proportions etc. Need to see a doctor as will require an examination and may require tests to sort it out.

Sudden?: If your buttock suddenly swelled up, it may be from angioedema which may be controlled with antihistamine. If the problem is a persistent or recurrent one, consult an allergist.