The pain you are referring to is in lower rib cage. It could be due to unaccustomed exertion. It is only 4 months since you had a Caesarean.
I suggest you go a little slow . You have been through a nine months pregnancy and a major surgery 4 months ago.
You should look after your Iron and
Calcium requirements, especially if you are feeding the baby. Please get your Haemoglobin also checked. You may consult a Gynaecologist on Practo with all the details.