Giok, Scotland doesn't have to join the euro. Look at Sweden's position.

Sweden does not have an opt-out from the euro but did not join ERM II and thus deliberately failed to fulfil the criteria for introducing the euro. Sweden later voted against euro introduction in a referendum in 2003, and the issue is currently dormant. The European Commission and the European Central Bank have stated they would tacitly accept this derogation for the time being. Swedish governments have repeatedly stated they will only introduce the euro after a referendum approving this move has been held.

At least with independence Scotland has a choice.