Creating magick with blood spells is a very old witchcraft, and though it is often associated with black magic, it's not really good or bad. Just powerful because it uses a vital part of your own body in the spell.
I already have one spell, Embrace the Shadows, that uses a drop of blood and here are a few more blood spells if you want to experiment with this sort of magick. Not for the squeamish.
Make Your Mark
This spell idea can be used for a mix of different purposes, as it is simply a magickal way of focusing your attention on a goal. This is a spell to make things happen, whether its in love, employment or anything else.
On the piece of paper, write out what you want to happen. Like I said, the purpose can be anything for this spell.
Underneath your words, draw this sigil:
Say the words of the spell:
By my own blood I swear,
Fire, Earth, Water, Air
Bind the powers to my need
With this magick, I do bleed.
Give your thumb a good jab with the pin to bring up a drop of blood. Press it down on the sigil to leave a fingerprint. Repeat the words of the spell again.
Sprinkle the pepper or ash over the damp spot, then blow the excess away. Now light the candle, and burn the paper. Pinch out the flame using your finger and the thumb you pricked.
Blocked by Blood
This is a protection spell, intended to protect your home from negative energy.
After the sun goes down, gather up your materials. If you can't get all the herbs, just make do with the ones you can acquire. You must have the garlic though.
Fill the cup with water, and then add the herbs and garlic. Give it a stir with your index finger. Now use that pin to jab the same index finger, and bring up a drop of blood. Mix the the water again, letting your blood wash off into the liquid.
Now go outside, declare that you are protecting your threshold, and pour the water into the earth as close to the door as you can.
If you happen to live in an apartment, and can't pour this out on your doorstep, you can modify the spell a bit. Take a little of the liquid and rub it on the door frame of your own apartment, and then pour the rest outside the main door of the building.
Note: for either of these spells, it would be a good idea to wash out your puncture wounds and get a bandaid on them when the rituals are finished. Always be safe when practicing blood spells.