battery/memory card slot cover is stuck

Did you review your owner's manual or review questions here for NK L310? Sometimes pressing down firmly on the battery cover before sliding the cover may help. A hard rap with a wooden or plastic handle with just enough force may break battery leakage creating the equivalent of instant glue bonding the cover to batteries. Any indication of battery leakage around the cover, apply some mineral/baby oil onto a Q-tip and gently swab around the cover perimeter may help loosen corrosion bonding the clover to the camera body. Use as little oil as possible, enough to allow it to work between the cover lines to seep into the dust seal. Let oil seep in then rap the cover a few times. Any excess oil can be absorbed with Q-tips or tissue. Hopefully, batteries aren't corroded but if the cover is removed to reveal corrosion, you may have to clean off corrosion on terminals after batteries are removed. De-Oxit is a product for cleaning battery corrosion on electrical contacts while promoting better connections.