Most people who are using TRT don't need to use it so be very dubious about what you're reading on the Internet. Testosterone is unfortunately abused. People are taking testosterone as a performance enhancer and a quick fix to get what they want. Look up "anabolic steroid abuse" or misuse if you want to see the side effects and problems with inappropriate use. Example include aggressive behaviour, mood swings, paranoia, cardiovascular effects that can cause heart attacks or stroke, kidney problems, infertility and small testicles. This is when you use extra testosterone on top of normal levels of testosterone.
Your case is very different and a lot of what you see online does not apply. In your case you have low testosterone - that is an actual medical condition and you're being prescribed testosterone to get up to normal levels. Having low testosterone can delay puberty, lead to low muscle mass, lead to reduced growth of the penis and testes, and lead to low sex drive, low energy, and long term infertity, erectile dysfunction and even osteoporosis.
If you've had a blood test showing you have low testosterone and are under a decent doctor who is prescribing this and monitoring it then you should follow their advice. You have a medical condition that should be treated for your benefit and quality of life. All the quackery from people who self medicate and abuse testosterone does not apply.