This does look like it may be from a shattered die from looking at your photos but it is probably just dried glue on the coin. If this is not dried glue and really is die breaks this coin would be worth quite a bit, but how much I'm not sure.
This is one of at least eight shattered obverse (anvil) dies known among 2007-P dimes. There are several stages in the breakdown of this particular die. If you can believe it, this is one of the earlier stages. It's a very nice error.
yes this is infact one of at least 8 i see 2 more in a simaler post but they were ms66 so they are perfect this one has been around, they were on ed weinburgs coins or something and was asking 750 for pair. i knew it was a pretty good find when i seen it . and it def the same dies that made his coins. pretty exciting to find something worth a lil money.