Thank you for your query,
Vomintings and loose motions are due to Gastroenteritis
may be a viral or bacterial cause.
These symptoms are not related to his hernia.
Because of increased intraabdominal pressure while vomiting os straining the size of hernia will increase.
For vomitings you can give antiemetic like ondansetron
in prescribed dosage.
Give sips of oral rehydrating solutions like Pedialyte ti prevent dehydration
Monitor his hydration status by his urine output, activity, and skin turgor.
Consult your Pediatrician
for the examination and specific treatment.
Hernis needs correction later, after taking the opinion of the Pediatric surgeon.
Hope I have answered your query.