that was very confusing to read. please rephrase so we can answer your question
I think that was a flashback. Like he is remembering how his mom and Law were working together with the whole "law's parents died" thing and maybe Jesse found out so he banned Law from coming there and so five years after that law shows up and gives him the moritat tea I'm pretty sure. I could be wrong but that's how I gathered it.
Oh I get it now here's wiyomi's explanation
this is "one day" since Jesse is out of Moritat project and back to reality.
yes, It refers to the present day.
This is why Jesse has pierce marks in his neck, he got this after being connected to Moritat's project .If you remember when Jesse comeback to reality (on chapter 32) Jesse disconnected this from his neck in a violent way.
You can check here.
http://www.mangago.zone/read-manga/moritat/uu/moritat-chapter-32/14/
http://www.mangago.zone/read-manga/moritat/uu/moritat-chapter-32/14/
There was no way he could have these marks before of being connected to Moritat.
Another proof this is the present day is the last page of chapter 50. Jesse said Law is a "talker" or how he only let him some inofensive pierced marks after all.
okay wait the nurse said one day is that also a flashback on when law showed up at jesse's school and jesse drank the tea? or is it on the present day? bc we saw on ch 50 that jesse pass out.