It is possible to safely and accurately administer your injectable medications in the privacy of your home. Safe injection practices protect the patient, the person giving the injection, as well as the environment. The two common types of injections administered at home are subcutaneous, which includes the administration of insulin, and intramuscular injections. If you must give yourself injections or give injections to a close friend or family member, you must first learn how to do so from the healthcare provider who is prescribing the medication to be injected.
You might have nicked a blood vessel, or even went through one. I have a lot of experience with injections, and I can feel when I am in a vessel, or drive through one. (I still pull back on the syringe to check for blood) But if I do hit a vessel, or go through one (on the surface, but inject into muscle) there is a slight swelling at the site. Even if you don't inject into a vessel, but nick or drive through one, there will be clotting. This might be your lump. But agian, only you can prevent forest fires ... I mean, only you can tell how serious it gets.