Dear friend, welcome to HCM!
Your child had a clear post-traumatic pleural effusion- ususally a bloody one called Haemothorax.
If it was not bloody, it is still a likely late effusion.
It is likely infected and hence the
fever and vomitting. Surprisingly culture failed to show any growth- which is possible and not rare.
Starting anti TB treatment seems unreasonable here and you should take
second opinion.
We do not start ATT without demonstrating
tuberculosis evidence.
And yours is a case of post traumatic effusion or and
empyema.
Try consulting a pulmonologist also and keep him on antibiotic cover. Please get a complete blood work done.
It could turn serious unless treated appropriately. TB is a rare possibility in this situation.
Take care and please keep me informed of your progress.
Good Luck!
I hope to have answered your query satisfactorily.
Thank you!