Oooh that pic is tiny weeny *lol*
Nuggets are notoriously hard to keep, with many dying in the first few weeks/early months of having them. Thing is they dont travel well, and take ages to acclimatise, by which point they can and do starve themselves. I lost mine this afternoon. I hate to say it, but he was hanging out around the filter too - despite having the extra airflow and current they like.
What are you feeding him? Have you seen him eating? Is his tummy hollow or his eyes sunken in?
Make sure you're offering fresh veg (courgette goes down well with most plecs) and some protein (shrimp pellets, bloodworm, squid pellets - something like that) as gold nuggets are omnivores and need that - as well as good pleco wafers. Nuggets like extra air flow (I think, but dont quote me, because they like higher temps and therefore need the extra oxygen), that's why many hang out round the filter or air stone - make sure you have one running in your tank, they'll appreciate it
Keep up with the maintenance, they're quite sensitive to bad water so it's important to keep up with water changes and gravel vacs.
After that it's just a case of sit back and see how it goes. There's only so much we can do, sometimes, like with mine, it just isn't enough. Fingers crossed yours is only there because he likes the current - and isn't poorly at all