There's no answer to this question, peppa....'cos guess what, it varies between individuals
Your experience is no more than slightly unusual - probably most women notice a difference between their breasts in the early days, weeks and months of bf, and your difference is probably more marked than most.
Time will make it less marked - supply usually regulates downwards, and both of your breasts will end up more like your right one, still supplying what your baby needs, without the extra fuss and flood and leakage
A guess would be that this will happen within a further 4-6 weeks.
Nothing really you can do about it - you could try to encourage him to feed from the right more, of course, but he probably knows what he likes best now.
My right boob is flabby soft and never leaks. It feels like ds can't be getting any milk from it, but he obviously is. Am happy w this boob. My left boob is about 2 cup sizes bigger and floods day and night (so I have to change). It is fairly hard and the milk sprays out. This makes ds cross, but it's still his favourite side. Ds is 6 weeks. Is there anything I can do to help balance this?