Suggest Remedy For Sore Penis Tip And UTI

Question: Hi! I have an 8 year old boy who just diagnosed with his first Urinary Tract Infection. His only symptom is pain sore tip of penis when urinating. I saw redness and a little wound on the tip of his penis which resolved within 2 days. However I brought him to his GP anyway and he was diagnosed to have balanitis and did a Urine test. In the meantime waiting for the urine result, I washed penis with saline water and applied antiseptic cream. A couple of days later, the urine result came and showed 5 in pH, Nil for Protein, Ketones, Glucose, blood and bilirubin. 1x 10^6/L for leucocytes and 0 for erythrocytes, epithelial cells and casts. As for for culture, an organism called Morganella Morganii is shown as >10^8 orgs/L. So based on the result my son was prescribed Bactrim oral suspension for 5ml/day. I was told to do another urine sample after the antibiotic is completed and an ultrasound soon after.
Now, I am sick worried about the end result, especially thinking there is an ultrasound involved. Is it very dangerous to have a UTI for an 8 year old boy for the first time? I read from the internet that there are diagnostic methods may be performed for a UTI such as VCUG and others. They are all scared me and making me worried. I am very concerned now. I am not really prepared should he need to undergo VCUG because it sounds so invasive. His only symptom was sore penis when he weed and it looked it resolved quickly without any antibiotic (the soreness was resolved before Bactrim was prescribed). I am very concern if he has kidney scarring etc. Please help I am very worried and the ultrasound is not going to be done in another week as he is still taking Bactrim. It makes me feel ill thinking of all the possibilities can take place. Many thanks.

Thank you! I really do hope the ultrasound result will be normal. I am very worried as the information I gathered from the net is that UTI can have no symptoms at all and yet project such a concerning health issue.