The short answer is you won't really have caused yourself any harm with doing this. IMHO 12.2 is a touch high but not going to be a real problem - how many tablets did you take and did you have any starchy carb as well?
The longer answer is that you need to treat hypos and in the early days will usually err on the side of over treating. If long term you have very erratic sugars that are rocketing up and down, then no, that's not great. However if you keep things reasonably controlled, then occasional spikes will not harm a T1.
Hypos can be very serious and you should aim to have as few as possible, but I think they are pretty much inevitable on insulin. When I started on insulin, I'd been very high for a while and 3.8 or 3.9 felt really worrying. Now, I'm a bit more relaxed about that. I still treat a hypo but you can get to be a bit more gentle handed once you've got more comfortable with everything.
Having lots of hypos and levels that are running too low can reduce your hypo sensitivity, i.e. the point at which you start to feel the symptoms but this can be fixed. If you aren't doing so, keep a record of your levels and track how many hypos you get.
