LOL, just replace it already. It's an inexpensive consumable item.
If you've got mold there, it's also likely that you also have additional mold cheerfully growing in the tiny inaccessible holes in the exhaust diffuser shown in the background too. (Those little holes that necessarily must remain clean and and open in order for respiratory exhalation and excess PAP exhaust air to exit the mask.)
It's also worth noting that the elbow shown in your photo is the older
AirFit F20 Elbow design anyway, which is much noisier in operation than the newer and quieter
AirFit F20 QuietAir Elbow design released in 2018.
Either are only $20 USD and are readily available online from a variety of sources.
In the future the best way to prevent mold from growing in the replacement elbow, and in your hose too, is to clean them frequently with mild soap and water.