For chronic pain and mild effusion from an old injury, short-term use of oral nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen can help reduce both pain and joint swelling. Alternatively, applying a topical NSAID gel, such as diclofenac, directly to the ankle is highly effective with fewer side effects. For pain relief without anti-inflammatory action, paracetamol is a safe option. Since this has persisted for 2.5 years, medication should only be a temporary aid. I highly recommend consulting an orthopaedic specialist or physical therapist to evaluate if ankle instability is causing the ongoing oedema and to guide your recovery.