Thank you for an interesting question. There are creams available that contain local anesthetics which numb the skin and these are used for anal health conditions such as anal sores or haemorrhoids (piles; dilated anal veins). These creams are only available with a prescription from a doctor or nurse.
I would not recommend using these types of creams for sex. They are designed for specific health conditions which have been properly researched and there is good evidence that using the creams will help. The creams were not designed for anal sex.
Pain during anal sex is usually not normal. Some discomfort is common, especially if the bottom is not properly relaxed and not enough lubricant has been used. I would suggest using more lubricant, having more foreplay before sex which includes anal play such as fingering or using dildos before sex. This will help relax the anal muscles as much as possible to avoid pain during sex.
If this does not help, I suggest you attend your nearest gay-friendly clinic to perform an anal examination to exclude any health condition that might be increasing pain during sex, and to advise you further about safe, comfortable and enjoyable anal sex.