1990 nickel with E Pluribus Unum on the back and it has a p on the front and the rest of the nickel looks just like any other nickel Is this worth anything or just the 5 cents it is?

Please take the time to look at the rest of the nickels in your pocket change! ALL nickels made since 1980, and about half of them made between 1968 and 1979, will have a mint mark near the date. P or blank = Philadelphia, D = Denver, S = San Francisco (only 1968-70)

So the small P means you have one of the 661,636,000 nickels struck in Philadelphia that year, and it's only worth 5 cents.