It sounds like you had some kind of injury that has become inflamed and possibly infected. I would definitely stop plucking the hairs around it as this will irritate the area further, and cutting a slit in something that is not an abscess
just causes more damage to an area that is already inflamed. Before doing anything more I would go see a doctor
who can examine the lesion more thoroughly and suggest how best to treat it and let it heal.
In terms of what caused the lesion in the first place, there are a couple possibilities. Constant chafing or low-level irritation, such as from a belt or a pair of pants, can cause the skin to become irritated and to thicken or to become red and irritated. It is also possible to have an ingrain hair that becomes inflamed or infected; this will usually be smaller, protrude outward, and drain with pressure. It is also possible to have a small abscess or cyst, but these would also drain a whitish liquid rather than bleed. Other possibilities include various different rashes and a superficial skin infection called cellulitis. Without seeing the lesion it's impossible to know which of these possibilities is most likely, but in any case it does sound like your interventions may have further aggravated the situation. I would leave it alone, put a clean bandage over it, and see your primary care doctor
as soon as possible.