First, I am so sorry to see the state of his mass for your lad. I do wish I could say that a cone is all he needed, but unfortunately I have to be honest and say that this appears much more serious.
Now I have to say that I strongly advise you do not try to lance this again. It does not look like an abscess at all and cutting into it will cause him pain and likely trigger infection itself. Instead, you will need to just bathe the open wounds with a mild antiseptic +/- use an OTC antibiotic cream until they heal.
Otherwise, I'd be more concerned that we either have benign growth
that is overgrowing (potentially arising from a dysplasia of hair or gland tissue) or a tumor (ie sarcoma being our main suspect if cancerous) that has been slow growing up until now. The dark discoloration will be related to the skin being under pressure and stretch from this (a combination of hyperpigmentation but also bruising from the stretch. And the problem with this is no matter what kind of mass we have (cancer or benign), this growth is going to continue until it causes that skin to ulcerate. And when that happens, it will become a constant battle to keep the bacteria on his skin from spreading inward and causing him discomfort, infection, and recurrent issues with abscesses. So, this is truly less then ideal situation.
Now I do appreciate the difficult position that you are in and that this is bad timing. Unfortunately, growths don't take this into consideration. So, while the cone and topical care will help heal the skin sores and the cone will protect what he may do to it (and we need to be careful since the stretching of skin is uncomfortable and dogs will sometimes rip these growths open and cause even more issue), the only real intervention for something like this is surgical. There just isn't anything OTC or medical that can reduce mass size.
So, it is a poorly timed urgent situation for him. Since you noted financial difficulties, I do want to note that if you wanted to have him seen there is a chain vet practice called VCA veterinary hospitals (http://www.vcahospitals.com/main/offer) that offer a free first consult offer. This would allow you to have he seen for free, which could offset the cost of having a sample take to diagnose what this is. Otherwise, in this situation, it may be worth checking the Humane Society's database. They have a lot of branches nationwide, along with ties to other assistance organizations, that can keep down costs and subsidize care (http://www.humanesociety.org/animals/resources/tips/trouble_affording_pet.html). And that may be the best option for getting him seen but also getting this treated in this unfortunate situation.
Please take care,