9 kg in a 10 month old is good.
Usually we say, a baby triples his birthweight
by 1 year of age.
Did you check his length? When your son becomes tall, you might feel he has grown thinner.
If there is no weight loss
, you need not worry.
Good that you are already giving him solid foods.
Restrict milk to 2 to 3 times in a day.
Aavin milk can be started after 1 year of age.
Milk of course has protein, calcium etc.... but its not the only thing needed for growth. Giving more milk will be of no good to your child. Just 2 to 3 glasses in a day is sufficient.
Fortify all the solid food you give with ghee/ oil. You may introduce dry fruits and nuts slowly.
Give him mashed fruits/ mashed vegetables instead of juice/ soup.
Till he is playful and gaining weight, you need not worry.
After 1 year of age, he will enter a period of slow growth. Also he will become more playful and he might start becoming picky in eating too.
Usually babies are about 10 kg at 1 year and 12 kg at 2 yrs.
Hope you find my answer helpful.