It seems like you were shot with a strange Arrow, because you have gained a Stand, a manifestation of your life energy as a visualization of your psyche! It's one that fits you and will likely integrate and hold similar mechanics to other powers you may have, but be warned, if you're weak willed, this very well could kill you. Of course, your descendants will also have a Stand and the same dangers apply to them, plus the fated attraction of Stand Users.
Generally speaking, it's said that only a Stand can beat other Stands since the only thing known to affect Stands would be other Stands, but in truth, that's not entirely the case. High-level powers like Scion's Stilling and Sting are actually able to affect Stands despite their ghost-like nature due to their own esoteric nature.