Westcoin is trying but he is actually describing two different types of error and then attributing your coin to the wrong one.
The letter P in the die was sunk into the die with a post inside the loop of the P. That post is what forms the "hole" in the loop of the P on the struck coin. On the die that created your coin that "post" has chipped off allowing metal from the planchet to fill the center of the loop and give it that blob appearance.
If the hole in the die had filled with grease, metal filings etc like Westcoin sugggested then the metal would not have flowed into the hole in the die and the P itself would have disappeared.
The problem comes from poor use of language when we are describing the coins. When a letter disappears from grease filling the letter we say it was a filled die, but when a die chip like yours causes that blob appearance people tend to call it a filled letter when actually the letter has not "filled" at all. There is actually MORE empty space in the die than there should be.