Swollen testicle on baby ?

Silvia

Went to his well check today and they told me he had swelling in the left testicle. She held a light up to it and said it’s likely just extra fluid but that we need to make sure to keep an eye on it and if it changes we need to do an ultrasound. Has anyone dealt with this? I googled it and it sounds like a hydrocele but my mind is racing that it could be something worse.