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1.The most possible cause according to your description seems like sebaceous
cyst, collection due to sebaceous duct blockage, they never cause malignancy but can cause infection if gets squeezed or disturbed, no need active treatment.
2.Next possible cause is hair follicular infection with collection within.
3.Finally localised skin inflammatory changes. which needs a course of antibiotics.
4.In all above cases advise you not to disturb the lumps - you will only complicate it. Maintain local hygiene, clean with antiseptic liquid.
5.Mean while visit your GP and get examined and get treated accordingly. Good luck.
Hope i have answered your query.
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http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888 Thank you.