I've been watching my betta for the last half hour or so, and he's only using one of his pectoral fins while the other is clamped to his side!!! Other than that, things seem normal... he's dancing around for me like he normally does (and is doing really well at it given he's only using one fin!), and he ate his breakfast (2 Hikari Gold pellets) normally a few hours ago. His color looks good, and he's not gasping for air or swimming strangely, from what I can tell, except that he's not using the one fin. I see him use the clamped fin once in a while, just for a second, and then clamp it back to his side, and it doesn't look torn. I'm very concerned that he's injured. Any idea what could be wrong and if there's anything I can do?
A little background: he's probably 6mos. - 1 year old, he lives in a 1 gallon bowl, unfiltered, we do 50% water changes daily to keep it fresh and clean, and we use Prime. There are no sharp ornaments in his tank, only flexible and soft fabric plants, and he is the only fish in the bowl.
Any advice is so appreciated, I'm so worried about my little guy! Thanks in advance.