Help! Click lock floor separation issue

I had a contractor lay down a click lock engineered floor last month. It looked fine but I should have looked closer because last night I noticed that almost in the middle of the living room there is one edge of a board that is up slightly. It seems that this particular board was not locked properly to it’s partner. While it is not so severe yet I worry it could get worse. Do I have to undo half the floor to fix this? That would be a nightmare. I was thinking to get a thin nail and nail the corner down and then stain the nail head after-words to hide it but I fear it might actually split the wood getting it it altogether. Also since a month has gone by I am not sure it is the contractors fault or some fault of the board itself. I paid the contractor a day wage and now I hate to ask him to come and spend a day undoing the entire floor. That will be an unpleasant holiday request.