There is no reasonable way to answer this question my friend. I need to ask if there is a possibility that you might be experiencing some kind of paranoia as a result of stimulant usage. If that is the case, I would seriously suggest taking a break from the stimulants. I'm not trying to patronize or belittle you. It's just that this would be considered a very common focus of worry for someone on a stimulant binge; bugs on the skin, particles in the rig etc.
At any rate, we definitely do not have the means to identify what these specs are and we can't tell you whether or not you are safe to inject said particles. It's just outside of what we are capable of. Don't take it personally. If we could identify the problem and help you, we would.