• ببخشید پشتم به شماست /bebakhshid poshtam be shomast/

It is not very polite to sit in front of someone who is older than you are when your back instead of your face is in her direction. (You are not face-to-face). Then if it happens for example in a car, you sit in the front seat, and the older person sits in the back seat, you can use it. You can say, “excuse me for my back is in your side” (word for word translation).

• خواهش میکنم (اشکالی نداره) ، گل پشت و رو ندارد /Khahesh mikonam (eshkali nadare), gol poshto ru nadare/

Also s/he can answer you kindly and politely “never mind, flower doesn’t have back and forth”