Follow Boozer then crawl under the fallen tree trunk. Continue to the path and squeeze through between the rocks. Use your Survival Vision to find the clue on the ground. Press and hold Square to examine it.
Follow the path ahead until you reach a Camp where Leon ambushes you. After the short cutscene, continue following him until you finally catch up to him. Another cutscene will follow.
After the scene, backtrack to the Camp and find the necessary materials needed to craft a bandage. Search the immediate area for a rag and sterilizer. Use your Survival Vision to locate them easily. Once you have the materials, press and hold L1 to open The Weapon Wheel, then craft the bandage. After crafting the bandage, use it immediately by pressing R2. Make your way back to your bikes to complete this mission and start the following one immediately.