first thing first, why not try and go for alternative approach i.e. seeing a chiropractor?

second, building muscle takes time. its all about progressive overload. if 4 kg's the max you can lift for now, then lift the 4 kg. its better than just complaining that you can't lift. if the 4 kg hurts, then lift 2 kg. if you're at a point that you can't even lift that weight, then you should not even do any sort of weight lifting and should focus on recovering properly first.