There was a conflict today. I lost the plot and said stuff I regretted. This caused a meltdown, followed by the silent treatment for many hours. How do I now reinstate normal /any conversation? Or do I have to wait for the BPD person to come to me when ready?
There's no hard and fast rule that works in every situation, so you're going to have more insight than we do on the timing.
As a general rule of thumb though, if you crossed a line then it's okay to apologize for your part and what's valid. If that brings more tension, then back off and give them space to process on their own timelines.
With my BPD daughter, sometimes an apology from me is the end of it and sometimes it's simply the beginning. We can only do our parts though and see where it leads. Also, be sure to give yourself some grace...we all explode at times.