Just use your hands
I feel as though a lot of people who eat sushi treat it with a bit too much reverence. All though sushi is a misleadingly complex topic, both for the chef and the customer, in the modern day, it is just meant to be enjoyed rather than over-analyzed.
If you have reservations or concerns that sushi has a "right and wrong" way of eating, you may be over-thinking it. One habit that I have picked up that is totally fine (and in fact the classic way of eating) is to just use my hands to eat nigiri sushi. I have discovered that there are many reasons for this practice, and also why it just makes sense.
I recently heard from an older sushi chef that sushi is Japan's original fast food, with both high and low quality options. Nigiri sushi is literally just a quick bite if you have some fish and some rice, so trying to over-beautify sushi is in some sense getting away from its roots. Also, nigiri sushi is best enjoyed when the slice of fish is immediately cut off from the fish steak, so using your hands to grab it and eat it shows that you are concerned with having the fish when it is still as moist as possible.
Also, it is advisable to not apply soy sauce directly to the rice, so you can imagine that using chop sticks can be a bit tricky if you follow this guideline. Grab the rice by the sides with your thumb and index finger, turn it upside down, and dip only the fish gently in the soy sauce and quickly bring the piece of sushi to your mouth to eat in one bite. Grabbing only the fish with the chopsticks, dipping it, and then transferring it back to the rice, and then grabbing the nigiri sushi with your chopsticks is time consuming, and you will likely drip soy sauce onto the counter.