erasor

Hi i have been riding a Yamaha Sr 125 for the past 5 months with no problems occuring, until today, i came into the garage and found that the key was in the ignition switich and was set to "on". the wierd thing is that no lights were showing while it was on, i turned it to off and turned it on again and go no electrics showing. due to this i thought that the battery had run flat, i placed it onto a recharger. it registered that the battery didnt need recharging, i have looked at the 20amp fuse and it is ok, the only other issue is that withing the last week is that when i would put my key into the ignition it was very stiff and wouldnt turn to on, i placed loads of 3 in 1 oil in adn it freed up and the bike started as normal. If anyone has any ideas on what the issue is it would be a great help. thankyou Karl