1 gallon boiling vs. 2 gallons

I recently made a stupid mistake and used a 1 gallon pitcher that I thought was two gallons and made my wort with only one gallon of water. went through the whole boiling process and didnt realize it until after i had put it into the bucket and had to add almost 4 gallons of water instead of 3 to fill it to 5 gallons.

My question is, will that make a difference on the outcome? will it be too weak? should I start over?

I assume you’re doing extract? OG is dependent on volume and sugars, so as long as you ended up with 5 gallons and you used all the extract, the gravity will be dead-on. You will likely have slightly poorer hop utilization, but otherwise it should turn out just fine.