If the goal is to indicate that Nelson is skilled at his hobby, a better word to replace "tinkering with" would be "practicing" or "deliberately experimenting with." These words convey a sense of purpose and intentionality, suggesting that Nelson spends time honing his skills and exploring new techniques or approaches in his hobby. "Tinkering" may suggest a more haphazard or casual approach, which could be interpreted as a lack of skill or expertise.