But if your blood sugar is ok, it’s fine. When we used to use syringes, I’m sure sometimes I drew up varying amounts as you’re aiming to get the insulin on the appropriate black line, but the line has thickness so, depending on exactly where on the line the insulin is, there must have been fractions of units missing - but it didn’t matter!
Your basal is 2 units - that’s what you need, right? But that’s not true. Maybe one night you need 1.87 units or another night you need 1.90. Perhaps you had a stressful day and you had a tad of lingering stress which pushed your needs up to 2.1? Who knows? The blob could just appear when you withdrawn the needle due to the change in pressure (not being in your flesh anymore) - that is, it’s not part of your dose, just an extra bit leaking out after the injection.
Even if you sorted this, you’d find something else to fret about. I say that not as a criticism but as something to keep in your mind. Anxiety is an awful thing and when it’s bad it can change your way of thinking. Taking control by rationalising it, by questioning it, by gently mocking yourself, by whatever works for you, can help.