Hi,Dear thanks for the query to HCM virtual clinic.
I studied your query in full details updated from you.I understood your health concerns.
Based on your query data, In my opinion ,Dear Your baby seem to suffer from -Non-Lipmatous lump on your shin,as its tender lately with 
redness over last 3 weeks.
In My opinion,you need to rule out the 
Varicose Veins of shin.Color doppler with dual image USG would fix the cause and would fix line of further treatment.
Other possibility of Sebaceous 
Cyst needs to be ruled out.
Surgeon would be  needed to fix these health issue with you.
Hope this reply would help you to evaluate your case and treat it with your doctors in time to come.
Hope this would resolve your query and worry and 
Anxiety accompanied with it.
Welcome for any further query in this regard to ME.I would love to help you out.
Awaiting for any further query.
Wish you fast recovery from this intriguing health problem.
Have a Good Day.
Dr.Savaskar M.N.
M.S.Genl-CVTS -Senior Surgical Consultant