There could be a number of things that could cause lesion on the skin like that- the bunny definitely needs to see the vet as soon as they are open. It could have been caused by a bite from another rabbit (do you have another rabbit?) any other type of puncture wound or even possibly an external parasite depending on your location/weather/etc (cuterebra).
It is impossible to tell the amount of damage from a photo- the wounds needs to be flushed and explored by a vet to determine the best course of treatment- sutures, sutures/drain or if risk of infection is too high- healing by second intention- leaving the wound open to granulate in and heal. How much damage the underlying tissue has sustained will need to be evaluated.
The bunny will most likely be prescribed antibiotics and pain meds along with the medical treatment- so there is really nothing you can do at home other than encourage the bunny to eat and drink until you get the rabbit to the vet ASAP.
If this is an abscess it would have resulted from an injury that happened weeks ago- and has finally gotten to the point where it has ruptured thru the skin. The initial injury could have been a single puncture- resulting in 2 draining wounds over the course of x amounts of weeks of festering under the skin- or the initial wound could have been 2 puncture wounds. Puncture wounds have a high rate of abscessing because they trap bacteria in, while healing over at the surface of the skin.
Please keep us updated and let us know what the vet says!