A few weeks ago, I landed in Dublin to visit my partner and friends that I have in Northern Ireland. On seeing that I had previously been a UK resident, the immigration officer asked me lots of questions. She then asked if I would be staying in ROI at any point during my trip, to which I responded "no." I explained that I would be staying at my partner's house in Belfast, Northern Ireland.
After this she put this stamp and written annotation in my passport:
I just noticed it today. What does it mean? I am applying for a fiancé visa next week for the UK and I want to avoid any issues. Should I be worried about this?