Blackhead is a yellowish or blackish bump or plug on the skin and is a type of acne vulgaris. It is caused by excess oils that have accumulated in the sebaceous gland's duct.
Cleanse the area thoroughly and apply a good mild exfoliating scrub on that. Apply a medicated cream or gel containing resorcinol, salicylic acid or benzoyl peroxide. This helps is soaking the oil and helps in peeling away the blackheads.If benzoyl peroxide leaves your skin dry, apply an oil-free moisturizer after 10 mins of applying benzoyl peroxide.
If the symptoms still persist then please consult a dermatologist and get cysts ruled out.
I hope it helps. Take care and regards.