If you get numbers very close to 4 while on insulin, you should reduce your dose again.
Some people on here find that they tolerate that sort of food very well also on type 2 on minimal treatment, so it makes sense to me.
You inject insulin to control your blood sugar not because you 'have to take a certain dose' so go by what your meter tells you.
Generally, you want to be at +2 mmol after a meal compared to before. If you're high to begin with, this of course changes a bit, but personally, I'd want to be around 5.5-6.0 2 hours after a meal, not 4.3 on insulin.
This should allow a little room for your BG to drop slightly more until lunch (if you don't snack) and before lunch would then be in the 4.5-5.5 range which is pretty sensible.
So no, don't be concerned, you're doing it fine. Just adjust your insulin so you don't go too low (normally defined as below 4.0, you may get symptoms (shakiness, blurry vision, irritability) anywhere between 4.5 and 3.5 at which point you should treat it with something sugary (which is better to avoid, and can be dangerous if not treated). So well done for getting it down there, now as you 'don't have a headache, don't take the headache pill' or at least not as much of it.
Keep something on hand until you know that you won't go too low. As your insulin will be injected and not turn off itself when your blood sugar drops, having a couple jelly babies, a biscuit or glucotabs on hand is a good idea.
-M