What is this movable ball-like lump in my left buttock after an ovarian cyst?

Given your description, this movable ball-like lump could be a lipoma, which is a benign, fatty growth commonly found under the skin. Lipomas are usually soft, painless, and can be moved around under the skin and they don’t typically bring about any discomfort or interfere with daily activities. This lines up with your symptoms as you mention no pain and they do not seem to affect your routine significantly. Another possibility, though less likely, could be a sebaceous cyst, which is a closed sac under the skin filled with a cheese-like or oily material. These can sometimes reduce in size without intervention. It’s important to keep in mind that not all lumps are harmless, so even though it doesn’t cause pain, a proper examination by a healthcare provider is wise. If it changes in size, becomes painful, or starts to affect your movement or general health, you should promptly seek medical attention. For now, since it has been stable over the year, you might prefer to simply monitor it for any changes. When you consult with a healthcare provider, they may opt for a physical examination and potentially an ultrasound or CT scan to get a clearer understanding of what exactly you’re dealing with. It’s unlikely related to the ovarian cyst you had last year, as lumps associated with hormonal or ovarian conditions typically don’t present in such a manner. Remember not to try and self-diagnose, or remove it yourself. Prioritize having it checked by a professional who can offer a more precise diagnosis. Since it doesn’t seem urgent or painful, checking in with a healthcare provider at your convenience would be sensible.