Hi omnomnonny, it is pretty likely that your pill is back to providing its contraceptive effects after the missed day, however do check the information leaflet that comes in the box for your particular one to see their instructions on how to handle a missed pill for the kind you take, and how long the manufacturers recommend using a backup method of contraception for after that.
This is because the different brands of pill have different levels of synthetic hormone in each dose and it is a medicine that works from it's cumulative effects (being taken on successive days). This is why you are still protected on the "inactive pill" days, why it's important to take them as regularly as possible, and why the different kinds will have different instructions to follow for a missed day. You can read more about this here:
How do birth control pills really work, even during the placebo period? and here:
Quick Hits: Questions and Answers on The Pill.
As Sofi said, spotting is a common pill side effect. People can often get extra side effects like this temporarily when something about the dosage fluctuates a bit, like a pill being missed or an extra dose from taking two in a day, like you had. As you are back to your usual timing taking the pill, you should likely see the spotting clear up soon and will likely find after reading the information leaflet that you are already covered for hormonal contraception again.
Using condoms as a back up is a good idea in any case for their STI protection, and when used together with the Pill gives you 98.7% effective protection from unintended pregnancy with typical use, so it's a great combo. You can read more about this here:
The Buddy System: Effectiveness Rates for Backing Up Your Birth Control With a Second Method.