It also really depends on the style of beer you were brewing. Undershooting your efficiency means that the beer is going to have a little less maltiness and body than expected, and the hops may come through a little more. If this was an American Pale Ale, it will be fine. If it was something that requires real balance, like a Dortmunder, then you might find it a bit off.
It is always a good idea to have a bit of dry malt extract (and some brewing software!) on hand for AG brewing, especially when you are starting out. That way, you have the option of 'topping up' your wort with extract to hit your target OG.