#4. "RE: D7000 sensor artifact/problem - help needed" In response to In response to 0
Your sensor would benefit from a professional clean. You can do it yourself if you a confident about doing it - but the kit may cost as much as having it professionally cleaned once. Digressing the inbuilt sensor cleaner normally removes dust very well. It can be set to clean the sensor each time you switch the camera on.
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.