Most kids who work from home from an early age (especially in creative fields) do tend to get isolated, because the comfort of the routine at home ends up being more appealing than the effort of going out. That said, at 16 there's an important difference between being more of a homebody and actually being trapped in isolation patterns that are bothering him. It's worth asking directly: does he not want to go out because he prefers staying where he is (which is legitimate), or because he's afraid or anxious when he thinks about going out? The answer changes the whole picture.
If he says he avoids social activities because of anxiety, physical discomfort, or because he thinks it won't work out, then yeah, it makes sense to look for a psychologist. Doesn't need to be a dramatic diagnosis at first; sometimes it's just someone external, not his dad "pressuring" him, to help him notice patterns. But if the kid is genuinely happy, productive with his work, and just doesn't feel the need to go out, maybe the problem is more yours than his (and it's okay to say that).
In the meantime, take the pressure off "social obligations." Instead of "you have to go to the beach," try something smaller and specific: "I'm going to a café tomorrow afternoon, want to come?" without making it a big deal if he says no. Sometimes an isolated teenager feels judged and that just pushes him further away. If he keeps rejecting everything completely for months, or if you notice changes in his mood, appetite, or sleep, then it's time to talk to a professional without further delay.