Shkodran Mustafi scored the opener with a header from a free kick, but Spurs argued that the goal was offside and that the free kick should never have stood.
Sanchez ended up scoring the winner for Arsenal, inflicting a second defeat in three league games for Spurs.
"I do not need to say anything, it was obvious for everyone here and watching at home," Pochettino told Sky Sports News. "It is not easy to accept because we lost the game but we have to more on and keep going.
"The free kick for the first goal and the first goal was obvious offside, maybe the second was too. When you play against a team in the top six, the big details are up to you, sometimes things go against you but that is football.
"Granit Xhaka should have had a second yellow card. Sometimes you feel disappointed and frustrated because the small details change a lot."
Tottenham have dropped to fourth in the table.