Dr Dick’s response: Basically everybody has a “tight” anus, since we are not born with an anus that’s “ready for action”. That means that one has to be “prepared” first before being penetrated, and especially so when it happens for the first time. The best way to be “prepared”, is when your partner uses his finger to first stimulate the anus to relax it a little and slowly begin to enter his finger into your anus.
Use a lot of water-based lube in the process. I would suggest that that could be enough for the very first time, and slowly work your way towards being penetrated by your partner’s penis the second or even third time you attempt being penetrated. It may be a little painful when being penetrated, especially the very first time.
The key is to take it very slowly. Enter the penis slowly and just a little (tip of the penis) at first, until you feel comfortable and then continue a little further. Should you feel too uncomfortable and it is too painful, rather stop, and try again another time. Be aware that a percentage of men have a condition that causes the anus not to be able to “open” up for penetration.
Haemorrhoids can be caused by penetration, but more damage can be done if you are not careful and you do not take it slowly. This, however, is usually because of rough sex where people are not taking it slowly and carefully. If your partner’s is very thick, you could rather try with a dildo first.
The saying goes: Age is but a number. If the age difference doesn’t bother the two of you, then it should be fine.